Using inattentional blindness as an operational definition of unattended: The case of surface completion

Studying inattentional processing is made difficult by the fact that measuring it often results in observers attending to the stimuli in question. Here it is suggested that inattentional blindness—the lack of awareness of stimuli that appear in unattended regions of the visual field—be used as an operational definition of unattended. Separate online measures, taken while the stimuli are still present, can then be used to probe specific aspects of processing. Applying this method to the perceptual completion of partial surfaces, an online measure of modal and amodal completion was developed, and then used within an experiment in which inattentional blindness to the surfaces was assessed. The results indicated that surface completion can be engaged by unattended stimuli. More generally, the study illustrates the usefulness of this approach for probing what processing does and does not occur for stimuli that appear in unattended regions of the visual field.